Over the past three months, there have been several episodes of increased earthquake activity at Iliamna Volcano. One of these episodes is currently ongoing, and is characterized by numerous small earthquakes. This increase in earthquake activity may be related to movement of magma at depth, and additional observations including an airborne gas sampling and observation flight are being planned to help constrain this interpretation. A similar, but longer episode of increased earthquake activity occurred from September 1996 to February 1997. It was likely related to the intrusion of new magma at depth, but an eruption did not occur.

AVO will continue to observe Iliamna carefully and will report on new observations and interpretations as warranted.

Iliamna Volcano is located on the western side of lower Cook Inlet in Lake Clark National Park and Preserve. The volcano has a summit altitude of 3053 m (10,016 feet) above sea level and the volcanic edifice supports an extensive cover of snow and glacier ice. An active fumarole field is present on the upper eastern face of the volcano and on calm days, vapor emissions are often visible. There have been no known historical eruptions of Iliamna Volcano, but volcanic deposits preserved on the flanks of the volcano indicate that there have been multiple episodes of explosive eruptive activity in the past 2500 years. Occasional large ice and rock avalanches, and changes in glacial ice have been observed in the past at Iliamna, but are not directly related to volcanic activity. The volcano is located 210 km (130 miles) southwest of Anchorage and 100 km (60 miles) northwest of Homer.

The Alaska Volcano Observatory is a cooperative program of the U.S. Geological Survey, the University of Alaska Fairbanks Geophysical Institute, and the Alaska Division of Geological and Geophysical Surveys.

VOLCANO ALERT LEVELS

NORMALVolcano is in typical background, noneruptive state or, after a change from a higher level, volcanic activity has ceased and volcano has returned to noneruptive background state.

ADVISORYVolcano is exhibiting signs of elevated unrest above known background level or, after a change from a higher level, volcanic activity has decreased significantly but continues to be closely monitored for possible renewed increase.

WATCHVolcano is exhibiting heightened or escalating unrest with increased potential of eruption, timeframe uncertain, OR eruption is underway but poses limited hazards.

WARNINGHazardous eruption is imminent, underway, or suspected.

AVIATION COLOR CODES

GREENVolcano is in typical background, noneruptive state or, after a change from a higher level, volcanic activity has ceased and volcano has returned to noneruptive background state.

YELLOWVolcano is exhibiting signs of elevated unrest above known background level or, after a change from a higher level, volcanic activity has decreased significantly but continues to be closely monitored for possible renewed increase.

ORANGEVolcano is exhibiting heightened or escalating unrest with increased potential of eruption, timeframe uncertain, OR eruption is underway with no or minor volcanic-ash emissions [ash-plume height specified, if possible].

REDEruption is imminent with significant emission of volcanic ash into the atmosphere likely OR eruption is underway or suspected with significant emission of volcanic ash into the atmosphere [ash-plume height specified, if possible].